Insect and Disease Disturbances Correlate With Reduced Carbon Sequestration in Forests of the Contiguous United States

Brendan R Quirion,Grant M Domke,Kristina Serbesoff-King,Songlin Fei,Brian F Walters,Joseph E Fargione,John M Randall,Gary M Lovett,Leigh Greenwood

doi:10.3389/ffgc.2021.716582

Abstract

Major efforts are underway to harness the carbon sequestration capacity of forests to combat global climate change. However, tree damage and death associated with insect and disease disturbance can reduce this carbon sequestration capacity. We quantified average annual changes in live tree carbon accumulation associated with insect and disease disturbances utilizing the most recent (2001 – 2019) remeasurement data from National Forest Inventory plots in the contiguous United States. Forest plots recently impacted by insect disturbance sequestered on average 69% less carbon in live trees than plots with no recent disturbance, and plots recently impacted by disease disturbance sequestered on average 28% less carbon in live trees than plots with no recent disturbance. Nationally, we estimate that carbon sequestration by live trees, defined as the estimated average annual rate of above- and belowground carbon accumulation in live trees (diameter at breast height ≥ 2.54 cm) on forest land, has been reduced by 9.33 teragrams carbon per year (95% confidence interval: 7.11 to 11.58) in forests that have experienced recent insect disturbance and 3.49 teragrams carbon per year (95% confidence interval: 1.30 to 5.70) in forests that have experienced recent disease disturbance, for a total reduction of 12.83 teragrams carbon per year (95% confidence interval: 8.41 to 17.28). Strengthened international trade policies and phytosanitary standards as well as improved forest management have the potential to protect forests and their natural capacity to contribute to climate change mitigation.

Highlights

Both reductions in greenhouse gas emissions and increases in carbon (C) sequestration and storage by natural systems are necessary to ameliorate global climate change (Edenhofer et al, 2014)
Our most parsimonious model for National Forest Inventory (NFI) plot-level average annual change in live tree C, based on model selection using maximum likelihood, included the dominant disturbance type assigned to the plot, ecoprovince in which the plot is located, initial live tree C measurement on the plot, and state/county in which the plot is located as predictor variables (AIC = 359690, r2 = 0.14)
Our estimated annual reduction in live tree C sequestration capacity associated with forest insect and disease disturbance (12.8 Tg C yr−1) represents approximately 9% of the contiguous US’s total annual forest C sequestration and is equivalent to the carbon dioxide emissions from over 10 million passenger vehicles driven for one year [United States Environmental Protection Agency (US EPA), 2020; Domke et al, 2020b]

Summary

Introduction

Both reductions in greenhouse gas emissions and increases in carbon (C) sequestration and storage by natural systems are necessary to ameliorate global climate change (Edenhofer et al, 2014). In the United States (US), conservation, restoration, and improved land management could provide C sequestration equivalent to an estimated 21% of current net annual emissions (Fargione et al, 2018). United States (US) forests currently provide an estimated 149 teragrams (Tg) in net live tree C sequestration annually (Domke et al, 2020b). Given the magnitude of the US’s live tree C sink, significant attention has been focused on whether this capacity can be increased through improved forest management (Birdsey et al, 2006), avoided deforestation (Fargione et al, 2018), and/or reforestation (Domke et al, 2020a). The US forest C sink, including soils, standing and downed wood, and live trees, may be in jeopardy due to increasing levels of disturbance (Anderegg et al, 2015), conversion (Homer et al, 2020), and/or declining sequestration rates in old growth stands (Pugh et al, 2019)

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